Picosecond ultrafast ultrashort pulse electron gun

Abstract

The application discloses a picosecond ultrafast ultrashort pulse electron gun, which comprises a light excitation component, a pulsed electron beam emission component, a vacuum shell and an electrode wire; the light excitation component comprises an ultrafast laser and a reflector; the pulsed electron beam emission component comprises a cathode structure, a grid structure and an anode structure; the cathode structure, the grid structure, the anode structure and the reflector form an integral whole and are arranged in the vacuum shell; the grid structure and the anode structure are sequentially arranged opposite to the cathode structure and are separated from each other to form a vacuum gap structure; the cathode structure is provided with a cold cathode; the center of the grid structure and the center of the anode structure are respectively provided with a first through hole and a second through hole; the reflector is arranged in the vacuum shell and is arranged opposite to the anode structure and is located on the side of the anode structure away from the grid structure; the center of the reflector is provided with a third through hole, and the first through hole, the second through hole, the third through hole and the center of the cathode structure are located on the same horizontal line. The application has the characteristics of low power consumption, high efficiency, small size, fast response speed and integration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vacuum electron sources and vacuum electron devices, and particularly relates to a picosecond ultrafast ultrashort pulse electron gun. BACKGROUND

[0002] With the development of human society, in order to meet the clear understanding of the microscopic world and ultrafast processes, ultra-high space-time resolution electron microscopy imaging and spectroscopy techniques are being sought. At the same time, due to the development needs of the fields of aerospace, radar communication, national defense and military industry, and large scientific devices, the development of high-frequency radiation sources, free electron lasers, small linear accelerators, linear colliders and other technical equipment is also becoming more and more urgent. The electron gun is a key core component to realize the above-mentioned vacuum electron devices. For the above applications, one way can use slow wave, backward wave and other structures to modulate the uniform electron beam emitted by the traditional direct current electron gun into a clustered pulse electron beam; another way can directly feed electromagnetic waves into the electron gun to directly modulate the electron emission and output a clustered electron beam, thereby forming an ultrashort pulse electron gun with high brightness, strong current and low emission degree.

[0003] At present, the technologies that can realize the above-mentioned ultrashort pulse electron gun mainly include a hot cathode microwave electron gun and a photocathode microwave electron gun. Among them, the hot cathode microwave electron gun generates electrons through thermal emission, and introduces a resonant cavity structure inside the electron gun, and uses the alternating electric field established in the resonant cavity to accelerate to form a bunch. The electron beam pulse width is completely determined by the electron dynamics in the resonant cavity. However, the hot cathode microwave electron gun itself has the problem of electron back bombardment due to structural limitations, which will cause the change of cathode temperature and physical damage, affecting the stability and life of the electron gun; in addition, the hot cathode microwave electron gun also faces the problems of increased complexity and volume due to filament heating and cooling, reduced response speed due to preheating, adverse effects of thermal radiation on other internal parts of the device, relatively large electron energy dispersion, and the like. The photocathode microwave electron gun is generally considered to be a future high-quality electron source generation device. It generates electrons by high-power laser bombardment of a photocathode, and accelerates and leads out the electron beam under the regulation of a microwave field. However, such an electron gun is greatly limited by the quantum efficiency of the photocathode material, and the electron gun needs a high-power frequency-doubled mode-locked pulsed intense laser source (the excitation light intensity requires to reach 1 GW cm -2 -1 TW cm -2 Above), which has a complex structure, a large volume, harsh working conditions, a short life, and high device operation and maintenance costs.

[0004] On the other hand, with the development of nanotechnology, field emission pulsed electron guns based on cold cathode nanomaterials and radio frequency excitation field are also increasingly valued by researchers. Field electron emission does not need to heat the cathode to a high temperature, relies on a very strong external electric field to narrow the surface potential barrier of the cathode, so as to produce quantum tunneling and electrons penetrating the surface potential barrier of the cathode, and theoretically can obtain instantaneous electron emission without time delay. Such electron guns have high electron emission efficiency and strong controllability, but are limited by the frequency limitation of pure electronic excitation field, so that the generation of picosecond, femtosecond and even shorter ultra-short pulse width electron beams has not been truly realized so far. SUMMARY

[0005] The present application is to overcome the problems of large volume, complex structure, slow response speed, large electron energy dispersion and low sub-efficiency of the existing electron gun, and provides a picosecond ultrafast ultra-short pulse electron gun which can directly emit a pulsed electron beam with ultrafast response and ultra-short pulse width under the joint excitation of low light intensity ultrafast laser and bias electric field, and has the characteristics of low power consumption, high efficiency, small size, fast response speed and integrability.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is:

[0007] A picosecond ultrafast ultra-short pulse electron gun, comprising a light excitation component, a pulsed electron beam emission component, a vacuum shell and an electrode wire;

[0008] The light excitation component comprises an ultrafast laser and a reflector.

[0009] The pulsed electron beam emission component comprises a cathode structure, a grid structure and an anode structure with conductive properties.

[0010] The cathode structure, the grid structure, the anode structure and the reflector form an integral whole in the vacuum shell.

[0011] The grid structure and the anode structure are sequentially arranged opposite to the cathode structure and are spaced apart from each other to form a vacuum gap structure; the cathode structure is provided with a cold cathode having field electron emission characteristics; the center of the grid structure and the center of the anode structure are respectively provided with a first through hole and a second through hole.

[0012] The reflector is arranged in the vacuum shell and is arranged opposite to the anode structure on the side of the anode structure away from the grid structure; the center of the reflector is provided with a third through hole, and the first through hole, the second through hole and the third through hole are on the same horizontal line with the center of the cathode structure.

[0013] The cathode structure, the grid structure and the anode structure are connected to an external driving circuit through electrode wires, under the action of a bias electric field, the cold cathode on the cathode structure generates electron emission; meanwhile, the ultrafast laser emits an ultra-short pulse laser beam, which passes through the second through hole, the first through hole and fully covers the cold cathode surface on the cathode structure through the mirror at a certain angle and light intensity, and the cold cathode surface generates ultra-short electron pulses excited by the ultrafast laser and regulated by the bias electric field; the generated ultra-short pulse electron beam passes through the first through hole and the second through hole in the center of the grid structure and the anode structure in sequence, is extracted through the grid and accelerated through the anode respectively, and is emitted from the third through hole of the mirror and the side wall of the vacuum shell.

[0014] Preferably, the vacuum shell comprises a metal shell, a glass liner, an electrode flange, a glass window and an exhaust flange.

[0015] The glass liner is arranged on the inner wall of the metal shell and is used for insulation with the metal shell; the cathode structure, the grid structure, the anode structure and the mirror form an integral whole in the glass liner.

[0016] The metal shell is connected with the electrode flange, the exhaust flange and the glass window, and the vacuum shell is formed through exhaust and vacuum packaging.

[0017] The glass window is located on the other side wall opposite to the side wall where the ultra-short pulse electron beam is emitted from the vacuum shell.

[0018] The ultrafast laser is arranged outside the vacuum shell, and the ultrafast laser emits an ultra-short pulse laser beam which fully covers the cold cathode surface on the cathode structure through the glass window and the mirror.

[0019] Further, the electron gun further comprises a gun body shell, and the vacuum shell and the ultrafast laser are arranged inside the gun body shell.

[0020] Still further, the side wall of the gun body shell is provided with an electrode interface, and the electrode wires are connected to an external driving and control circuit through the electrode interface.

[0021] Preferably, the cathode structure, the grid structure, the anode structure and the mirror are made of metal materials and are separated from each other to form a vacuum gap, and the cold cathode is made of nanomaterials.

[0022] Further, the nanomaterials are ordered carbon nanotube films, disordered carbon nanotube films, upright few-layer graphene, tungsten and oxide nanomaterials of tungsten, molybdenum and oxide nanomaterials of molybdenum, or zinc oxide nanowires.

[0023] Preferably, the cathode structure and the gate structure have a spatial distance ranging from 0.01mm to 10mm; the gate structure and the anode structure have a spatial distance ranging from 0.01mm to 10mm; and the anode structure and the mirror have a spatial distance ranging from 10mm to 100mm.

[0024] Preferably, the electrode line is used to connect an external driving circuit, when using positive voltage driving, the voltage applied to the gate structure is not higher than 5kV, the voltage applied to the anode structure is not higher than 10kV, and the cathode structure is grounded.

[0025] When using negative voltage driving, the voltage applied to the gate structure is not lower than 0V, the voltage applied to the cathode structure is not lower than -5kV, and the voltage applied to the anode structure is not higher than 5kV.

[0026] The bias electric field between the cathode structure and the gate structure acts on the nanomaterial cold cathode on the cathode structure and excites electron emission.

[0027] Preferably, the wavelength of the ultra-short pulse laser beam emitted by the ultrafast laser ranges from 430nm to 2400nm; the output pulse width of the ultrafast laser ranges from 1ps to 5000ps; and the output spot diameter of the ultrafast laser ranges from 0.5mm to 2mm.

[0028] Further, the ultra-short pulse laser beam emitted by the ultrafast laser is irradiated at an irradiation angle ranging from 0° to 75° and an irradiation light intensity ranging from 10 0 W cm -2 -10 9 W cm -2 , and sequentially irradiates the cold cathode surface on the cathode structure through the second through hole and the first through hole.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] The present application uses a cold cathode excited by an ultrafast laser and a bias electric field, thereby generating an ultra-short electron pulse: on the one hand, the negative effects of the hot cathode microwave electron gun, such as electron back bombardment, large volume, complex structure, slow response speed, heat radiation, and large electron energy dispersion, are avoided; on the other hand, the advantages of the optical cathode microwave electron gun and the field emission pulse electron gun in obtaining transient electron emission, ultra-short pulse width, and low energy dispersion are exerted.

[0031] The application adopts a cold cathode with field electron emission characteristics, obtains high quantum efficiency, large current, high brightness, low energy dispersion of electron emission, greatly reduces the high requirements of the excitation light source of the ultra-short pulse electron gun, reduces the light intensity by at least more than 4 orders of magnitude, reduces the power consumption and size of the device, and greatly improves the integrability and miniaturization of the device. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a device structure schematic diagram of a picosecond ultrafast ultra-short pulse electron gun described in embodiment 1.

[0033] Figure 2 is an SEM and TEM morphology diagram of a carbon nanotube nanomaterial cold cathode with field electron emission characteristics described in embodiment 1.

[0034] Figure 3 is a time-domain waveform of an ultrafast electron pulse generated by a picosecond ultrafast ultra-short pulse electron gun described in embodiment 1.

[0035] Figure 4 is a relationship between the emission characteristics and the external quantum efficiency of a picosecond ultrafast ultra-short pulse electron gun described in embodiment 1.

[0036] Figure 5 is an emission current characteristic of a picosecond ultrafast ultra-short pulse electron gun described in embodiment 1.

[0037] Figure 6 is an electron transmittance of a picosecond ultrafast ultra-short pulse electron gun described in embodiment 1.

[0038] Figure 7 is an SEM and TEM morphology diagram of a vertical few-layer graphene-gold nanoparticle nanocomposite described in embodiment 2.

[0039] Figure 8 is an electron emission periodic time-domain waveform information of an ultra-short pulse electron gun recorded by a high-bandwidth oscilloscope described in embodiment 2, and a frequency spectrum line carried thereby.

[0040] In the figure, 10 is a light excitation component, 11 is an ultrafast laser, 12 is a reflector, 20 is a pulse electron beam emission component, 21 is a cathode structure, 211 is a cold cathode, 22 is a grid structure, 23 is an anode structure, 30 is an outer shell, 31 is a vacuum outer shell, 311 is a metal outer shell, 312 is a glass inner container, 314 is an electrode flange, 315 is a glass window, 316 is an exhaust flange, 32 is a gun body outer shell, 40 is an electrode line, 41 is a laser power supply line, 42 is a laser control line, 43 is a cathode electrode line, 44 is a grid electrode line, and 45 is an anode electrode line. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention and are only used for illustrative purposes and should not be understood as limiting this patent. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0042] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Example 1

[0044] like Figure 1 As shown, a picosecond ultrafast ultrashort pulse electron gun includes a light excitation component 10, a pulse electron beam emitting component 20, a vacuum housing 31 and an electrode line 40;

[0045] The optical excitation component 10 includes an ultrafast laser 11 and a reflector 12;

[0046] The pulse electron beam emitting component 20 includes a cathode structure 21, a grid structure 22 and an anode structure 23 having conductive properties;

[0047] The cathode structure 21, the gate structure 22, the anode structure 23, and the reflector 12 form a whole and are placed in a vacuum housing 31;

[0048] The gate structure 22 and the anode structure 23 are sequentially arranged opposite to the cathode structure 21 and spaced apart from each other to form a vacuum gap structure; a cold cathode 211 having field electron emission characteristics is provided on the cathode structure 21; a first through hole and a second through hole are respectively opened in the center of the gate structure 22 and the anode structure 23;

[0049] The reflector 12 is disposed in the vacuum housing 31 and is disposed opposite the anode structure 23 and located on a side of the anode structure 23 away from the gate structure 22. A third through hole is defined at the center of the reflector 12, and the first through hole, the second through hole, the third through hole, and the center of the cathode structure 21 are located on the same horizontal line.

[0050] The cathode structure 21, the gate structure 22 and the anode structure 23 are connected to an external driving circuit through an electrode line 40, under the action of a bias electric field, the cold cathode 211 on the cathode structure 21 generates electron emission; meanwhile, the ultrafast laser 11 emits an ultra-short pulse laser beam, which passes through the second through hole, the first through hole and fully covers the surface of the cold cathode 211 on the cathode structure 21 at a certain angle and light intensity, and the surface of the cold cathode 211 generates an ultra-short electron pulse excited by the ultrafast laser and regulated by the bias electric field; the generated ultra-short pulse electron beam passes through the first through hole and the second through hole in the center of the gate structure 22 and the anode structure 23 in turn, is extracted by the gate and accelerated by the anode respectively, and is emitted from the third through hole of the reflector 12 and the side wall of the vacuum shell 31.

[0051] It should be noted that the center of the cathode structure 21, the gate structure 22, the anode structure 23 and the reflector 12 is on the same horizontal line. The ultrafast laser 11 is a small ultrafast laser. The ultrafast laser 11 is a laser based on SESAM, Kerr lens and other mode-locked technologies, and the pulse width is in the order of ps or even fs.

[0052] The surface of the cold cathode 211 generates an ultra-short electron pulse excited by the ultrafast laser and regulated by the bias electric field; the generated ultra-short pulse electron beam passes through the through hole in the center of the gate structure 22 and the anode structure 23 in turn, is extracted by the gate and accelerated by the anode respectively, and realizes an ultra-short pulse electron beam with low power consumption, high efficiency, ultrafast response and ultra-short pulse width.

[0053] The cold cathode 211 excited by the ultrafast laser and the bias electric field directly emits an ultra-short pulse electron beam with ultrafast response and ultra-short pulse width, and the electron gun has the characteristics of low power consumption, high efficiency, small size, fast response speed and integrability: on the one hand, the negative effects of the hot cathode microwave electron gun, such as electron back bombardment, large volume, complex structure, slow response speed, heat radiation and large electron energy divergence, are avoided; on the other hand, the advantages of the light cathode microwave electron gun and the field emission pulse electron gun in obtaining transient electron emission, ultra-short pulse width and low energy divergence are exerted.

[0054] The cold cathode 211 with field electron emission characteristics is adopted, high quantum efficiency, large current, high brightness and low energy divergence of electron emission are obtained, the high requirement of the excitation light source of the ultra-short pulse electron gun is greatly reduced, the light intensity is reduced by at least more than 4 orders of magnitude, the power consumption and size of the device are reduced, and the integrability and miniaturization of the device are greatly improved.

[0055] In a specific embodiment, the vacuum shell 31 includes a metal shell 311, a glass inner container 312, an electrode flange 314, a glass window 315 and an exhaust flange 316.

[0056] The glass inner container 312 is arranged on the inner wall of the metal outer shell 311 to insulate the metal outer shell 311; the cathode structure 21, the gate structure 22, the anode structure 23 and the mirror 12 form an integral whole in the glass inner container 312.

[0057] The metal outer shell 311 is connected with the electrode flange 314, the exhaust flange 316 and the glass window 315, and is exhausted and vacuum packaged to form the vacuum outer shell 31.

[0058] The glass window 315 is located on the side wall opposite to the side wall from which the ultra-short pulse electron beam is emitted from the vacuum outer shell 31.

[0059] The ultrafast laser 11 is arranged outside the vacuum outer shell 31, and the ultrafast laser 11 emits an ultra-short pulse laser beam to irradiate the surface of the cold cathode 211 on the cathode structure 21 through the glass window 315 and the mirror 12.

[0060] The electrode line 40 includes a laser power line 41, a laser control line 42, a cathode electrode line 43, a gate electrode line 44 and an anode electrode line 45.

[0061] The cathode electrode line 43, the gate electrode line 44 and the anode electrode line 45 are respectively electrically connected with the cathode structure 21, the gate structure 22 and the anode structure 23 through the electrode flange 314. The laser power line 41 and the laser control line 42 are electrically connected with the ultrafast laser 11.

[0062] The laser power line 41, the laser control line 42, the cathode electrode line 43, the gate electrode line 44 and the anode electrode line 45 are used to connect external driving and control circuits to form the picosecond ultrafast ultra-short pulse electron gun.

[0063] In this embodiment, the vacuum outer shell 31 is exhausted and vacuum packaged through the exhaust flange 316, so that the vacuum outer shell 31 forms a vacuum. In this embodiment, the vacuum degree is 10 -5 Pa-10 -4 Pa order of magnitude.

[0064] In a specific embodiment, the electron gun further includes a gun body shell 32, and the vacuum outer shell 31 and the ultrafast laser 11 are arranged inside the gun body shell 32. In this embodiment, the shell of the electron gun includes the gun body shell 32 and the vacuum outer shell 31, wherein the vacuum outer shell 31 and the ultrafast laser 11 are arranged inside the gun body shell 32, and the ultrafast laser 11 is arranged outside the vacuum outer shell 31.

[0065] In the embodiment, the side wall of the gun body shell 32 is provided with electrode interfaces; the electrode line 40 is connected to the external driving and control circuit through the electrode interfaces. The laser power line 41, the laser control line 42, the cathode electrode line 43, the gate electrode line 44 and the anode electrode line 45 are respectively electrically connected to different electrode interfaces, and the laser power line 41, the laser control line 42, the cathode electrode line 43, the gate electrode line 44 and the anode electrode line 45 are electrically connected to the external driving and control circuit through the electrode interfaces.

[0066] In the embodiment, the gun body shell 32 can be made of plastic material.

[0067] In a specific embodiment, the cathode structure 21, the gate structure 22, the anode structure 23 and the mirror 12 are made of metal material and are separated from each other to form a vacuum gap; the cold cathode 211 is made of nanomaterial. The metal material includes brass or stainless steel material. The cathode structure 21, the gate structure 22 and the anode structure 23 are separated from each other by a ceramic insulator to form a vacuum gap.

[0068] Further, the nanomaterial can be an ordered carbon nanotube film with a low work function and a high length-diameter ratio, or a disordered carbon nanotube film, or an upright few-layer graphene, or tungsten and its oxide nanomaterial, or molybdenum and its oxide nanomaterial, or zinc oxide nanowire.

[0069] In a specific embodiment, the vacuum gap between the cathode structure 21 and the gate structure 22 is in the range of 0.01mm-10mm; the vacuum gap between the gate structure 22 and the anode structure 23 is in the range of 0.01mm-10mm; and the vacuum gap between the anode structure 23 and the mirror 12 is in the range of 10mm-100mm.

[0070] In a specific embodiment, the electrode line 40 is used to connect the external driving circuit, when using positive voltage driving, the voltage applied to the gate structure 22 is not more than 5kV, the voltage applied to the anode structure 23 is not more than 10kV, and the cathode structure 21 is grounded (-0V);

[0071] When using negative voltage driving, the voltage applied to the gate structure 22 is not less than 0V, the voltage applied to the cathode structure 21 is not less than -5kV, and the voltage applied to the anode structure 23 is not more than 5kV;

[0072] The bias electric field between the cathode structure 21 and the gate structure 22 acts on the nanomaterial cold cathode 211 on the cathode structure 21 and excites electron emission.

[0073] In a specific embodiment, the ultrafast laser 11 adopts monochromatic light output or continuous wavelength light output, and the wavelength range of the emitted ultra-short pulse laser beam is 430nm-2400nm; the output pulse width range of the ultrafast laser 11 is 1ps-5000ps; the ultrafast laser 11 adopts spatial light or fiber output, and the output spot diameter range is 0.5mm-2mm.

[0074] The ultra-short pulse laser beam emitted by the ultrafast laser 11 is irradiated via the reflector 12, and the irradiation angle range is 0°-75°, and the irradiation light intensity range is 10 0 W cm -2 -10 9 W cm -2 , sequentially through the second through hole, the first through hole, the surface of the cold cathode 211 on the cathode structure 21 is fully irradiated, so that the surface of the cold cathode 211 generates an ultrafast ultra-short pulse electron beam excited by the ultrafast laser and regulated by the bias electric field.

[0075] The device overall size of the picosecond ultrafast ultra-short pulse electron gun after vacuum packaging is about 40cmx10cmx10cm, which is suitable for portable and small device equipment applications. One side of the gun body shell 32 is provided with an electrode interface, and the electrode line 40 (including the laser power line 41, the laser control line 42, the cathode electrode line 43, the grid electrode line 44, and the anode electrode line 45) is connected to the external driving and control circuit through the electrode interface, and the driving electric field and control of the small ultrafast laser 11, the cathode structure 21, the grid structure 22 and the anode structure 23 are respectively applied.

[0076] The pulse electron beam emitting part 20 of the picosecond ultrafast ultra-short pulse electron gun adopts stainless steel machining, and the machining precision is 0.05mm, the diameter of each part is 3cm, and the thickness is between 1-2mm. Four positioning holes and one electrode hole are punched on each emitting part, the diameter of the positioning hole is 2mm, and the diameter of the electrode hole is 1mm. In addition, the grid aperture is 2mm, the anode aperture is 4.7mm, the vacuum distance between the cathode structure 21 and the grid structure 22 is 0.16mm, and the vacuum distance between the grid structure 22 and the anode structure 23 is 0.5mm.

[0077] Figure 2 The SEM and TEM morphology of the carbon nanotube nanomaterial cold cathode 211 with field electron emission characteristics in this example is shown in the figure. The carbon nanotube cold cathode 211 material is a 3-wall vertical carbon nanotube, and the height and diameter are both 1mm. Under the joint driving of ultrafast light excitation and bias electric field, a large amount of ultrafast ultra-short pulse electron beam can be emitted from the tip.

[0078] Figure 3The time-domain waveform of the superfast electron pulse generated by the picosecond superfast ultrashort pulse electron gun described in the present example. The wavelength range of the small superfast laser 11 is 430 nm-2400 nm, the laser pulse width is 100 ps, the average power is 0.24 W, and the peak intensity is 7.68 MW cm -2 , the incident angle is 40°; a negative pressure is used for driving, the cathode voltage is-550 V, the gate voltage is 0 V, and the anode voltage is 300 V; under the joint driving of the superfast laser and the bias electric field, the surface of the vertical carbon nanotube emits a periodic ultrashort pulse electron beam with a repetition frequency of 1 MHz and a pulse width of 278 ps, which proves the good emission performance of the picosecond superfast ultrashort pulse electron gun described in the present example.

[0079] As shown in Figure 4 , the relationship between the emission characteristics and the external quantum efficiency of the picosecond superfast ultrashort pulse electron gun described in the present example. Under the simulation conditions of a cathode voltage of-550 V, a gate voltage of 0 V, and an anode voltage of 300 V, an electron beam current of up to 575 μA and a quantum efficiency of more than 2.5‰ are achieved. This further proves the technical effects of the picosecond superfast ultrashort pulse electron gun described in the present example.

[0080] As shown in Figure 5 , the actual emission characteristics of the picosecond superfast ultrashort pulse electron gun described in the present example. Under the conditions of a laser intensity of 7.68 MW cm -2 and a bias electric field of 3.44 V μm -1 , a pulsed electron beam with an average current of 38 μA and a peak current of 137 mA can be generated, at this time the average current density is 0.12 A cm -2 , and the peak current density is 435 A cm -2 .

[0081] Figure 6 The electron transmittance of the picosecond superfast ultrashort pulse electron gun described in the present example. Under the joint driving of the superfast laser and the bias electric field, the electron transmittance decreases with the increase of the cathode-gate voltage, and its range is between 64% and 94%, which is better than the electron transmittance (59%) under the driving of a single electric field.

[0082] The picosecond ultrafast ultrashort pulse electron gun described in the embodiment adopts an electron gun structure excited by an ultrafast laser field and a bias electric field, avoids the negative effects of the hot cathode microwave electron gun, such as electron back bombardment, large volume, complex structure, slow response speed, heat radiation, and large electron energy dispersion, and simultaneously plays the advantages of the photocathode microwave electron gun and the field emission pulse electron gun in obtaining transient electron emission, ultrashort pulse width, and low energy dispersion; the nanomaterial cold cathode 211 with field emission characteristics is adopted, which not only obtains high quantum efficiency, large current, high brightness, and low energy dispersion of electron emission, but also greatly reduces the high requirement of the ultrashort pulse electron gun on the excitation light source, reduces the light intensity by at least more than 4 orders of magnitude, reduces the power consumption and size of the device, and greatly improves the integrability and miniaturization of the device.

[0083] Embodiment 2

[0084] Based on the picosecond ultrafast ultrashort pulse electron gun described in embodiment 1, that is, the same ultrashort ultrafast pulse electron gun as in embodiment 1 is adopted in the embodiment. Specifically, the nanomaterial cold cathode 211 with field emission characteristics described in the embodiment adopts Au-on-Gr Nanostructures; the small ultrafast laser 11 adopts a monochromatic wavelength of 525 nm to meet the plasmonic resonance band of the nanocomposite material, a laser pulse width of 250 ps, an average power of 12.35 mW, a peak light intensity of 5000 W cm -2 , and an incident angle of 45°; a positive voltage is adopted for driving, the cathode voltage is 0 V, the gate voltage is 1 kV, and the anode voltage is 6 kV; thereby further verifying the technical effect of the picosecond ultrafast ultrashort pulse electron gun described in the embodiment.

[0085] As shown in Figure 7 , it is an SEM and TEM morphology diagram of Au-on-Gr Nanostructures. In the embodiment, the vertical few-layer graphene film is transferred to the cathode structure 21 made of stainless steel, which effectively ensures good adhesion and uniformity; and the gold nanoparticles with surface plasmon resonance characteristics are deposited on the surface of the vertical few-layer graphene emitter by ion sputtering and high-temperature annealing process; under the driving of the external bias electric field, the vertical few-layer graphene film emits electrons from the tip; at the same time, under the excitation of the ultrafast laser, the electron emission is controlled by light to generate a pulse electron beam with ultrafast response and ultrashort pulse width.

[0086] Figure 8The periodic time-domain waveform information of the electron emission of the ultra-short and ultra-fast pulsed electron gun recorded by the high-bandwidth oscilloscope and the frequency spectrum line carried thereby are shown in the embodiment. By comparing the amplified single laser pulse waveform with the electron emission response waveform, it is shown that although the electron emission response pulse has a certain degree of delay and rising edge broadening, the time correlation relative to the ultra-fast laser excitation can be basically met based on the plasmon-mediated electron emission. The pulse electron beam obtained in the embodiment has an electron pulse width of about 600 ps, and the periodic time-domain pulse waveform is recorded in real time. Further, by using Fourier transform on the obtained time-domain waveform, it is obtained that the plasmon-mediated ultra-short pulsed electron gun described in the embodiment can carry a high-frequency signal of more than 12.5 GHz, which indicates the application prospect of the plasmon-mediated ultra-short pulsed electron gun in a high-frequency radiation source vacuum electron device above 10 GHz.

[0087] Obviously, the above-mentioned embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the implementation modes of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A picosecond ultrafast and ultrashort pulse electron gun, characterized by: It comprises a light excitation component (10), a pulse electron beam emission component (20), a vacuum housing (31) and an electrode wire (40); Wherein, the optical excitation component (10) includes an ultrafast laser (11) and a reflector (12); The pulse electron beam emitting component (20) comprises a cathode structure (21) having conductive properties, a grid structure (22) and an anode structure (23); The cathode structure (21), the grid structure (22), the anode structure (23), and the reflector (12) form a whole and are placed in a vacuum housing (31); The grid structure (22) and the anode structure (23) are sequentially arranged opposite to the cathode structure (21) and spaced apart from each other to form a vacuum gap structure; a cold cathode (211) having field electron emission characteristics is provided on the cathode structure (21); a first through hole and a second through hole are respectively provided at the centers of the grid structure (22) and the anode structure (23); The reflector (12) is arranged in a vacuum housing (31) and is arranged opposite to the anode structure (23) and located on a side of the anode structure (23) away from the grid structure (22); a third through hole is provided at the center of the reflector (12), and the first through hole, the second through hole, the third through hole and the center of the cathode structure (21) are on the same horizontal line; The cathode structure (21), the grid structure (22) and the anode structure (23) are connected to an external driving circuit through an electrode line (40). Under the action of a bias electric field, the cold cathode (211) on the cathode structure (21) generates electron emission. At the same time, the ultrafast laser (11) emits an ultrashort pulse laser beam, which passes through the reflector (12) and then, at a certain angle and intensity, passes through the second through hole and the first through hole in turn to fully cover the surface of the cold cathode (211) on the cathode structure (21). The surface of the cold cathode (211) generates ultrashort electron pulses that are excited by the ultrafast laser and regulated by the bias electric field. The generated ultrashort pulse electron beam passes through the first through hole and the second through hole in the center of the grid structure (22) and the anode structure (23) in turn, is extracted by the grid and accelerated by the anode, and then is emitted from the third through hole of the reflector (12) and the side wall of the vacuum shell (31).

2. The picosecond ultrafast and ultrashort pulse electron gun according to claim 1, characterized in that: The vacuum housing (31) includes a metal housing (311), a glass liner (312), an electrode flange (314), a glass window (315), and an exhaust flange (316); The glass liner (312) is arranged on the inner wall of the metal shell (311) for insulation from the metal shell (311); the cathode structure (21), the grid structure (22), the anode structure (23) and the reflector (12) form a whole and are placed in the glass liner (312); The metal shell (311) is connected to the electrode flange (314), the exhaust flange (316) and the glass window (315), and is exhausted and vacuum-sealed to form the vacuum shell (31); The glass window (315) is located on the other side wall opposite to the side wall from which the ultrashort pulse electron beam exits the vacuum housing (31); The ultrafast laser (11) is arranged outside the vacuum housing (31), and emits an ultrashort pulse laser beam which passes through the glass window (315) and the reflector (12), and then fully covers and irradiates the surface of the cold cathode (211) on the cathode structure (21).

3. The picosecond ultrafast and ultrashort pulse electron gun according to claim 1, characterized in that: The electron gun further comprises a gun body shell (32), and the vacuum shell (31) and the ultrafast laser (11) are placed inside the gun body shell (32).

4. The picosecond ultrafast and ultrashort pulse electron gun according to claim 3, characterized in that: An electrode interface is provided on the side wall of the gun body shell (32); the electrode wire (40) is connected to an external drive and control circuit via the electrode interface.

5. The picosecond ultrafast and ultrashort pulse electron gun according to claim 1, characterized in that: The cathode structure (21), the grid structure (22), the anode structure (23) and the reflector (12) are made of metal materials and are separated from each other to form a vacuum gap; the cold cathode (211) is made of nanomaterials.

6. The picosecond ultrafast and ultrashort pulse electron gun according to claim 5, characterized in that: The nanomaterial is an ordered carbon nanotube film, or a disordered carbon nanotube film, or upright few-layer graphene, or tungsten and its oxide nanomaterial, or molybdenum and its oxide nanomaterial, or zinc oxide nanowire.

7. The picosecond ultrafast and ultrashort pulse electron gun according to claim 1, characterized in that: The vacuum distance between the cathode structure (21) and the grid structure (22) ranges from 0.01 mm to 10 mm; the vacuum distance between the grid structure (22) and the anode structure (23) ranges from 0.01 mm to 10 mm; and the vacuum distance between the anode structure (23) and the reflector (12) ranges from 10 mm to 100 mm.

8. The picosecond ultrafast and ultrashort pulse electron gun according to claim 1, characterized in that: The electrode line (40) is used to connect to an external driving circuit. When a positive voltage is used for driving, the voltage applied to the gate structure (22) does not exceed 5kV, the voltage applied to the anode structure (23) does not exceed 10kV, and the cathode structure (21) is grounded. When using negative voltage driving, the voltage applied to the gate structure (22) is not less than 0V, the voltage applied to the cathode structure (21) is not less than -5kV, and the voltage applied to the anode structure (23) is not more than 5kV; The bias electric field between the cathode structure (21) and the gate structure (22) acts on the nano material cold cathode (211) on the cathode structure (21) and stimulates electron emission.

9. The picosecond ultrafast and ultrashort pulse electron gun according to claim 1, characterized in that: The wavelength range of the ultrashort pulse laser beam emitted by the ultrafast laser (11) is 430nm-2400nm; the output pulse width range of the ultrafast laser (11) is 1ps-5000ps; and the output spot diameter range of the ultrafast laser (11) is 0.5mm-2mm.

10. The picosecond ultrafast and ultrashort pulse electron gun according to claim 1, characterized in that: The ultrashort pulse laser beam emitted by the ultrafast laser (11) passes through the reflector (12) and is irradiated at an angle of 0° to 75° and an intensity of 10 0 W cm -2 -10 9 W cm -2 , sequentially passing through the second through hole and the first through hole to fully cover and irradiate the surface of the cold cathode (211) on the cathode structure (21).

Images